How to select a time zone from an ISO 8601 format string into a calendar instance
As input, I have a string, which is a string in ISO 8601 that represents a date. For example:
“2017-04-04T09:00:00-08:00”
The last part of the string, “-08:00”, represents the time zone offset. I converted this string to a Calendar instance as follows:
Calendar calendar = GregorianCalendar.getInstance();
Date date = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.US).parse(iso8601Date);
calendar.setTime(date);
ISO8601Date is “2017-04-04T09:00:00-08:00”
But this does not select the time zone,
if I get the time zone from the Calendar instance, it provides the current settings instance of the laptop and does not get the timestamp from the ISO 8601 string. I check the time zone through the calendar instance as:
calendar.getTimeZone().getDisplayName()
Can someone show how to select a time zone in a Calendar instance?
Solution
tl; dr
OffsetDateTime.parse( "2017-04-04T09:00:00-08:00" )
Details
The last part of String which is “-08:00” denotes TimeZone Offset.
Do not confuse the offset with the time zone.
-08:00 means offset-from-UTC , no time zone. Time zones are named after continents, slashes, and regions, such as America/Los_Angeles or Pacific/Auckland or Asia/Kolkata
You are using the troublesome old datetime class, now superseded by the java.time class. For Android, see ThreeTen-Backport ThreeTenABP project.
Your input indicates only the offset and not the region. So we resolve it as OffsetDateTime
OffsetDateTime odt = OffsetDateTime.parse( "2017-04-04T09:00:00-08:00" ) ;
If you are absolutely sure of the expected time zone, assign it.
ZoneId z = ZoneId.of( "America/Los_Angeles" ) ;
ZonedDateTime zdt = odt.atZoneSameInstant() ;
About java.time
placed in Java 8 and later within the java.time framework. These classes replace the troublesome old classes legacy datetime classes, eg java.util.Date , Calendar , & SimpleDateFormat .
Joda-Time project, now in maintenance mode, it is recommended to migrate to java.time class.
To learn more, see Oracle Tutorial. The specification is JSR 310
Where do I get the java.time class?
- Java SE 8 , Java SE 9, then
- Built.
- Part of a standard Java API with a bundle implementation.
- Java 9 adds some minor features and fixes.
- Java SE 6 and Java SE 7
- Many java.time features are backported to Java 6 and 7 in ThreeTen-Backport
- Android
- ThreeTenABP project is adapted specifically for Android ThreeTen-Backport (as described above).
- See also How to use ThreeTenABP….